1. Field of the Invention
The present invention pertains to improvements in heat pipes adapted to transport large amounts of heat over long distances with small temperature loss in the process
2. Description of the Prior Art
The need for improved heat transfer devices is exhibited most urgently in handling temperature problems in satellites employing solar cell arrays that are periodically subjected to sunlight and darkness where extremes of shifts in temperature exist. It is appreciated that in sunlight high temperatures can cause problems of structural integrety maintenance, and in darkness equally damaging cold temperatures are encountered.
One solution for the heat-cold cycles is presented in Wyatt U.S. Pat. No. 3,152,774 of Oct. 13, 1964 where the cyclic extremes in temperature are controlled within tolerable limits by utilizing the latent heat properties of certain materials, particularly the latent heat of vaporization. The construction proposed in this patent uses sufficient metal only for structural purposes and the desired thermal capacity is obtained by using a fluid coolant material such as water, methyl chloride, or one of the Freons. The thermal capacity is supplied by the specific heat of the fluid, and importantly by the heat of fusion or by the heat of vaporization thereof. The function of heat control is carried out with a textile, flock or fibrous material which acts as a wick to transfer fluid to the high heat zones for vaporization and to zones of low temperature for condensation to the fluid state. The wick material is carried in light weight metallic structure, and the wick material is interrupted or is not intended to be continuous.
Another version of a heat pipe is disclosed in Kirkpatrick U.S. Pat. No. 3,735,806 of May 29, 1973 but in this device thermal energy is moved only in one direction corresponding to the gravitational force acting thereon. The transfer of thermal energy is by the convection process in one direction in which the exposed surfaces are thermally insulating and the internal structure has insulating properties and capillary structure has a high thermal impedance and becomes an isothermal evaporator.
Other devices in the heat pipe class are Eastman U.S. Pat. No. 4,274,479 of June 23, 1981; Asselman et al U.S. Pat. No. 3,811,496 of May 21, 1974; Paine et al U.S. Pat. No. 3,603,382 of Sept. 7, 1971 and Levedahl U.S. Pat. No. 3,498,369 of Mar. 3, 1970.